EP0226946A1 - Method for continuously making webs for the building industry - Google Patents

Abstract

1. Method for the continuous production of webs for the building industry with use of moulded pieces, more particularly made of thermoplastic plastics materials, by which 1. the moulded pieces are poured with the aid of a pouring apparatus on a continuous transportation apparatus to form a layer with largely constant layer height, 2. the moulded piece layer is pre-heated, 3. the pre-heated moulded piece layer is compressed under the action of heat and pressure to form a homogeneous web, 4. and the compressed, homogeneous web is cooled under the action of pressure, characterised in that 5. during the compression process and also during the cooling, a pressure, which, in each case, is largely uniform and constant, is continuously exerted on the web and in that subsequently 6. a layer of the cooled web close to the surface is removed.

Description

The invention relates to a method for the continuous production of sheet goods for the building industry according to the preamble of claim 1.

Flooring and wall coverings and in particular those made of thermoplastic materials are understood to be web products for the construction industry in the sense of this invention. The preferred area of application is the production of directionally patterned floor and wall coverings based on PVC.

Shaped pieces in the sense of this invention are in particular chips, crumbs, sections, pieces or chips made of suitable starting materials.

From DE-B2-19 28 405 a process for the production of patterned floor coverings is known, in which a mixture of differently colored chips of thermoplastic materials is rolled out into a web and then combined with other webs and calendered. With this method, only sheets of small thickness can be produced, since voids occur in the case of larger thicknesses due to air pockets. Furthermore, rolling and calendering process steps generally lead to a directional structure of the resulting patterns.

From DE-PS 637 144 a method for the production of floor coverings is known in which a rubber mixture or the like. is guided between two circulating belts around a vulcanization drum and cooling drums, three drums being arranged in an S-shape, so that the pressure exerted by the belts on the covering remains approximately constant from the beginning of the heating period to the end of the cooling phase. However, this document gives no suggestion for a method or a device for the production of sheet goods from thermoplastic materials and accordingly has no influence on the technical development in this area.

From DE-C2-3D 31 839 a process for the production of patterned webs made of thermoplastic material is known, in which particles, e.g. chips, crumbs, sections, pieces or chips are continuously poured onto a carrier tape to form a raw layer, the raw layer is preheated and then pressed and welded qua ^g -continuously using pressure and heat and then cooled under the action of pressure. A pressure of approx. 10 to 60 bar is applied periodically by a (double) vibratory press, alternately the material is transported step by step and quasi continuously. The periodic mode of operation should avoid the occurrence of voids in the web material thus produced. The disadvantage of this method is that only a low working speed of at most 2 m / min can be achieved. With large covering thicknesses and when using larger fittings, voids occurred in the interior of the webs despite the use of periodic pressing. Due to the necessary high pressure and the periodic pressure, expensive and complex constructions were necessary. Furthermore, this working process required high temperatures in order to achieve void-free work results. In the case of thick layers in particular, the contours of the particles used were washed out in the finished web.

From DE-A1-26 36 170 a double belt press is known in which two endless, driven metal belts are guided over deflecting rollers in such a way that between the metal belts a band-shaped layer of a material to be treated is first passed over a heated and then a cooled roller. An approximately constant pressure is constantly exerted on the material web. There is no indication in this document of the suitability of this double belt press for the method according to the invention.

The object of the present invention is to improve a continuous process for the production of sheet goods for the construction industry in accordance with the preamble of claim 1 such that no voids occur even at higher production speeds, that even under unfavorable conditions (large denomination of the chips, high working speeds, etc .) sharply defined boundary lines of the fittings used can be reached. The process should be able to be implemented with simple constructive measures.

According to the invention, this object is achieved by the characterizing features of claim 1.

Chips, crumbs, sections, pieces or chips, in particular made of thermoplastic, can be used as shaped pieces. Suitable thermoplastics are, in particular, vinyl polymers and / or copolymers of vinyl chloride, such as, for example, polyvinyl chloride, containing plasticizers and, if appropriate, other auxiliaries, such as stabilizers, pigments, fillers. Mixtures of particles of different thermoplastic materials or else plastic mixtures can also be used, thermoplastic materials such as acrylates, polyesters, ethylene-vinyl acetate being used.

The shaped pieces can each have different colors and / or can preferably be patterned in themselves.

Moldings which are produced by extrusion and moldings which are produced by punching or chipping from raw rolled skins are particularly suitable. Balls (0 from 2 to 30 mm), cubes (2 to 30 mm edge length), disks with a thickness of 1 to 5 mm with a rectangular or round shape with lengths of 2 to 60 mm are considered as preferred shapes.

The various fittings can be used individually, but preferably mixed from two to four types.

The shaped pieces are poured in a cold or preheated / still warm state with the aid of a pouring device onto a conveyor belt to form a layer with a largely constant layer height. The layer height should preferably correspond to 1.5 to 3 times the average dimensions of the fittings. Good results are obtained with bed heights of 8 mm to 50 mm, in particular 10 to 20 mm.

The molding layer can then advantageously, e.g. using a doctor blade, a shaker, or a spiked roller, be mechanically equalized and pre-compressed.

The molding layer is then preheated. 80 ° C are sufficient as the preheating temperature with a low bed height and appropriate design of the pre-device, but the molding layer is advantageously pre-sintered at a higher temperature. This takes place at an average temperature of approx. 130 ° C, preferably an average temperature of the continuous web of 150 ° C to 170 ° C should be reached at the end of the sintering section. Uniform heating up to the middle of the molding layer is advantageous. Temperatures above 180 ° C generally do not lead to better work results.
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Following the preheating or pre-sintering of the molding layer, it is continuously compacted to a homogeneous web under largely constant and uniform pressure in the thermoplastic state and then cooled while maintaining the pressure. It has surprisingly been found that a uniform pressing process can withstand the slowly pulsating pressure influence, e.g. according to the method according to DE-C2-30 31 839, is superior. Unexpectedly, there are no voids in the method according to the invention, even when using large shaped pieces and at high working speeds of more than 8 m / min.

During the pressing, the preheated or pre-sintered web in the pressing device, preferably on both sides, is heated to temperatures in the range from 170 ° C. to 220 ° C., preferably to temperatures from 175 ° C. to 185 ° C. The setting of the temperature depends on the dwell time of the web in the pressing device, on the thickness of the web, on the material of the shaped pieces and on the pressing pressure exerted. It has surprisingly been found that a pre-pressure of approximately 3 bar to 9 bar leads to excellent results. The pressure is preferably 5 bar to 7 bar. Favorable residence times have been found to be 0.3 minutes to 1.5 minutes, preferably 0.5 minutes to 1 minute. Production speeds of more than 8 m / min could be achieved.

According to the invention, a largely uniform pressure is exerted on the web during pressing and during cooling. It is crucial that the pressure never falls below a minimum value of approx. 1.5 bar to 2 bar (absolute).

The cooling under the action of pressure should take place at least to such an extent that the temperature of the web is below the softening temperature of the plastic material used. Advantageous it cools down to temperatures from 70 ° C to 90 ° C. Temperatures of 65 ° C to 75 ° C have been found to be favorable for optimal web withdrawal from the steel belts of the pressing device, for example.

The cooled web is homogeneous and void-free, but shows a slightly smeared structure of the surface design. It has surprisingly been found that this mixed color formation and fuzzy limitation of the contours of the moldings used is limited to a layer close to the surface. After removing a layer of approximately 0.1 to 0.5 mm, preferably 0.15 mm to 0.25 mm, the design appears extremely sharply defined and clear. It is advantageous that the structure appears uniform in all directions, so that the direction of production is no longer recognizable on the surface image. The layer near the surface can preferably be removed by grinding.

After the layer close to the surface has been removed, further work steps can be used, such as splitting, tempering, polishing, etc. It has been found to be advantageous that web products produced by the process according to the invention show only an extremely low tendency to shrink, so that tempering can possibly be omitted.

An advantageous device for performing the method according to the invention is specified in claims 12 to 14.

An embodiment of the invention is shown in the drawing and will be described in more detail below.

• Figur eine Einrichtung zur Durchführung des erfindungsgemäßen Verfahrens.

It shows the

• Figure a device for performing the method according to the invention.

For a first test example, patterned chips from a rolled raw hide of approx. 2 mm thickness in a circular shape with 5 mm and 10 mm 0 and in a rectangular shape of 5 mm × 10 mm were used. These shaped pieces 1 are mixed and fed onto a first conveyor 3 by means of a feed device 2. This conveyor consists of an approximately 10 cm to 20 cm wide conveyor belt which is rotatably mounted and carries out pivoting movements across the width of the following conveyor 4. This second conveyor 4 reserves over a distance of, for example, 0.5 m to 1.5 m in order to achieve a uniform bed on the continuous transport device 7. The bed is leveled and pre-compressed by means of a pin roller 5. The average bed height in the first test example is approx. 2.5 mm. The metal conveyor belt 74 of the continuous transport device 7 was heated by a heater 72 and by the roller 73 to a temperature of about 180 ° C. At the same time, the molded piece layer 6 was heated from above with a heating device 8 by means of radiant heat. The molding layer was heated to an average temperature of 160 ° C, the individual moldings being pre-sintered into a coherent porous web. A double belt press 9 with a heating drum 94, a cooling drum 95, a metal belt 92, which was driven by a deflection roller 93, and a metal belt 91 indirectly driven by the plastic web 10 by frictional engagement was used as the compression and cooling device.

The tensile stresses of the approximately 1.5 mm thick metal strips 91, 92 and thus the pressures on the web in the heating zone or in the cooling zone can advantageously be regulated or controlled separately by hydraulic adjustment of the rollers 98.

In the exemplary embodiment, the pressure in the area of the heating drum 94 was set to approximately 6 bar (corresponds to 7 bar absolute) via the metal strip 91, the pressure in the area of the cooling drum 95 was 3 bar (corresponds to 4 bar absolute). It is crucial that the pressure in the area of the cooling drum does not fall below a value of approx. 1.5 bar to 2 bar (absolute), otherwise blowholes can be expected. Higher pressures require a correspondingly high level of design effort.

The transition between the heating drum 94 and the cooling drum 95 takes place under relatively low pressure, but this is not critical insofar as the tension of the belts 91, 92 is still sufficiently high. The diameter of the cooling drum 95 and the heating drum 94 was 630 mm in the exemplary embodiment with a width of 600 mm in each case. In the first test example, the production speed was 2 m / min.

In the first test example, an idler belt 12 was introduced onto the continuous transport device 7 via the roller 73. This idler belt 12 consists of dense Kevlar fabric and is removed from the supply roll 121 and, after the pressing, is pulled off the web 11 and wound up with the take-up roll 122 in order to be used again later. It is also possible to return the idler belt directly to the deflection roller 73. Furthermore, a second idler belt can optionally also be inserted from above between the preheated or presintered web 10 and the metal belt 92 of the double belt press 9.

The heating in the heating drum 94 via the oil-fired heating drum 94 having a Ö1- flow temperature of 195 ⁰ C, over the preheated band 91 and on the heating means 96 to heat radiation. The belt 91 is heated to a temperature of 185 ° C. via the heated roller 99. The maximum temperature of the web was approximately 180 ° C. in the transition area between the heating drum 94 and the cooling drum 95.

The cooling drum 95 is water-cooled from the inside. In addition, this area is externally cooled by the cooling device 97 e.g. cooled by cold air. The average temperature of the web at the end of the cooling section at point A was approximately 75 ° C. and at the withdrawal of the web from steel belt 91 (point B) approximately 70 ° C.

The thickness of the web was determined to be approximately 2.4 mm before entry into the double belt press 9, and when the web 11 was pulled off (point B) it was approximately 2.2 mm. The surface structure was slightly washed out and out of focus.

The cooled web 11 is ground on one side to a final dimension of 2 mm by means of a grinding device (not shown). This resulted in a sharply defined, direction-free pattern.

In a second exemplary embodiment, shaped pieces with an average characteristic dimension of 2 to 5 mm are poured into a shaped piece layer 6 with an average dumping height of 8 mm and treated as in the first test example. The thickness of the web after presintering was approx. 7 mm, the production speed was 1 m / min.

The compressed web 11 had a thickness of 5.5 mm. This was ground down on both sides by 0.25 mm each. The finished sheet with a thickness of 5 mm showed a clear structure and a direction-free pattern. With a further device with drum diameters of 2000 mm, a third exemplary embodiment is carried out with the same test conditions as in the first example. The production speed is 6 m / min, the finished web of 2.2 mm before grinding or 2 mm after grinding results in the same pattern as in the first version example.

In a fourth embodiment, a double belt press with a drum diameter of 2000 mm is used, the same fittings as in the second embodiment and the same dumping height as in this example being used. With the exception of the production speed, which in this example is 3 m / min, all other process conditions and results remained identical to those of test 2.

Using correspondingly larger drum diameters leads to correspondingly increased production speeds.

Claims (14)

1. Process for the continuous production of sheet goods for the building industry using molded parts, in particular made of thermoplastic materials, in which 1. the shaped pieces are poured with the aid of a pouring device on a continuous transport device to a layer with a largely constant layer height, 2. the molding layer is preheated, 3. The preheated molding layer is compressed to a homogeneous web under the action of heat and pressure 4. and the compressed, homogeneous web is cooled under the action of pressure,
characterized in that 5. During the compression process and during cooling, a largely uniform and constant pressure is constantly exerted on the web and that subsequently 6. A layer near the surface of the cooled web is removed. 2. The method according to claim 1, characterized in that the molding layer is pre-sintered by appropriate heating to form a coherent, transportable web. 3. The method according to claim 2, characterized in that the presintered web has an average temperature of 130 ° C to 18D ° C, preferably from 150 ° C to 170 ° C. 4. The method according to any one of claims 1 to 3, characterized in that the shaped pieces have a different geometric shape and / or a different size in thickness, length and circumference. 5. The method according to any one of claims 1 to 4, characterized in that the shaped pieces are patterned in themselves. 6. The method according to any one of claims 1 to 5, characterized in that the layering of the shaped pieces takes place on the continuous transport device by means of a reversing conveyor. 7. The method according to any one of claims 1 to 6, characterized in that the reversing conveyor is fed by another conveyor which changes over its width. 8. The method according to any one of claims 1 to 7, characterized in that the molding layer is mechanically leveled and pre-compressed before preheating or pre-sintering. 9. The method according to any one of claims 1 to B, characterized in that the preheating or presintering of the molding layer is carried out by the action of heat from the heated conveyor belt of the continuous transport device and / or by the action of heat from above. 10. The method according to any one of claims 1 to 8, characterized in that the preheating or presintering of the molding layer is carried out by an alternating electromagnetic field in the interior of the fittings. 11. The method according to any one of claims 1 to 10, characterized in that an idler belt, in particular an aramid fabric, is introduced between the continuous transport device and the molding layer, which is withdrawn from the compressed web after it has cooled. 12. Device for performing one of the methods according to one of claims 1 to 11, with a double belt press for compressing the preheated or presintered web and then cooling the compressed web under the action of pressure, characterized in that the double belt press (9) has two endless metal belts ( 91; 92), the metal strips (91, 92) each being guided around deflecting rollers (93, 98) and holding the preheated or presintered web (10) between them over a certain range of their length, the metal strips (91 , 92) together with the intermediate web around a heated treatment drum (94) and then around a cooling drum (95), and both metal strips (91, 92) are also under such tensile stress that a largely uniform and constant pressure is exercised on the web. 13. The apparatus according to claim 12, characterized in that the metal strip (92), which is guided inside the heated treatment drum (94) inside and in the cooling drum (95) outside, by one of the deflection rollers (93) or by the heated treatment drum ( 94) is driven, while the other metal strip (91) is driven indirectly by frictional engagement over the intermediate path. 14. Device according to one of claims 12 or 13, characterized in that the metal strips have a thickness between 1 and 2 mm.

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